$ git clone -n https://src.fedoraproject.org/rpms/xrdb.git /var/lib/mock/f45-build-39142-732/root/chroot_tmpdir/scmroot/xrdb
Cloning into '/var/lib/mock/f45-build-39142-732/root/chroot_tmpdir/scmroot/xrdb'...
$ git fetch origin 46d4e35215d658b1ba51748cc4c18778d5b95cf1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xrdb
 * [new ref]         46d4e35215d658b1ba51748cc4c18778d5b95cf1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 46d4e35 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild